The use of silicon dioxide as a reinforcing filler in tyre compounds has been known for some time due to its advantages in terms of rolling resistance and roadholding on wet surfaces.
Silicon dioxide is used to partially or totally substitute carbon black. The use of silicon dioxide entails a series of drawbacks due to the difficulty of dispersion of the silicon dioxide in the polymer base. Said problem derives from the presence on the silicon dioxide of surface silanol groups, which favour the formation of hydrogen bonds and, therefore, agglomerates of silicon dioxide particles, and give the silicon dioxide hydrophilic characteristics which have poor compatibility with the hydrophobic characteristics of the rubber. A poor dispersion of the silicon dioxide in the rubber compound prevents total exploitation of its advantages, especially in terms of rolling resistance.
In order to solve the dispersion problems described above, the use of silane bonding agents has been known for some time; these inhibit the formation of the above-mentioned hydrogen bonds bonding with the silanol groups and, at the same time, chemically bond the silicon dioxide to the polymer base.
In the tyre industry the need is particularly felt to find solutions able to give the tyres an increasingly low rolling resistance without compromising other properties of the compound.
As is known to persons skilled in the art, being able to guarantee an improved dispersion of the silicon dioxide in the compound would make it more effective in terms of rolling resistance and would consequently permit a more limited use of the silicon dioxide.
However, it has been experimentally ascertained that a reduction in the reinforcing filler produces a deterioration in the mechanical properties of the compounds despite contributing to an improvement in terms of rolling resistance.
The need was felt for a solution which produces in the tyres an improvement in the rolling resistance together with an improvement in the mechanical properties. In particular, the need was felt for a solution able to reduce the quantity of the reinforcing filler in the compound while guaranteeing an improvement in the mechanical properties together with an improvement in the rolling resistance.